Method of waste disposal



June 2, 1953 c, W,I RICE 2,640,807

METHOD OF WASTE DISPOSAL Filed March l0, i949 4 Sheets-Sheet 1 6L-f a[murali il, 7 @TM @wrm .97: L6 @VH1/97 June 2, 1953 c, w, RlcE 2,640,807

METHOD oF WASTE DISPOSAL Filed March 10, 1949 4 Sheets-Sheet 2 June 2,1953 c. w. RICE METHOD oF WASTE DISPOSAL.

Filed March 1o, 1949 4 Sheets-Sheet 3 [mn To NNN .GNN

Cytaa ldm. J

June 2, 1953 c. w. RICE; 2,640,807

METHOD oF WASTE DISPOSAL Filed March 10, 1949 4 Sheets-Sheet 4 WENTQIQCyan -/m ffice Patented June 2, 1953 UNITED STATES PATENT OFFICE METHODF WASTE DISPOSAL Cyrus W. Rice, Pittsburgh, Pa.

Application March 10, 1949, Serial No. ,80,727

4 Claims. 1

This invention relates to the treatment of acid and cyanide i-ndustrialWastes.

Acid and cyanide Wastes are formed adjacently in various industrialoperations. For example, in the steel industry pickling operations andcyaniding operations are sequentially performed on bodies of metal forplating with nickel, chrome or the application of other protective orornamental coatings. Wastes containing sulphuric acid or one of theother mineral acids are highly detrimental if present in streams insubstantial concentration and Wastes containing cyanides are poisonousto stream life and dangerous to human life if carried into streams inany appreciable quantity. Certainty in operations for disposing of thoseWastes is therefore a matter 0f necessity. Certainty in neutralizing theacid wastes and in combining or decomposing'the cyanide Wastes havingbeen assured, efficiency and economy in the methods of disposal aregreatly to be desired. Assuming that the reagents as for neutralizationand decomposition must be present in quantity in excess of thattheoretically required for those reactions, it is desirable to utilizethe reagents in as slight excess as gives certainty in disposal. Also itis desirA able, still within the bounds of safety, 'toy lnnimize thenumber .ofV tanks required for treating the wastes and for settling theproducts of the treatment.

One object of my invention is to insure com, plete neutralization of theacid Waste and to insure complete decomposition of the cyanide Waste.

Another object of my invention is te provide a system so safeguardedthat it is made certain a safe excess of the reagents 'for rendering thewastes harlnless Will at al1 times be supplied, and to minimize thequantity of reagents required for positive safety.

Another object of my invention is to provide simplied plant structure ofsuch sort that it re.- duces the initial cost of plant installation,While also attaining the other objects of my invention relating to themaintenance of assuredly safe conditions with a minimum expenditure ofreagents.

Another object of my invention is to provide a system for disposing oiindustrial wastes of the type indicated above which is under automaticand correlated control of both the intake of wastes to the system andthe supply of requisite reagents thereto to maintain safe conditions,and automatically to safeguard the supply of reagents.

2 It may be stated generally that in attaining the objects of myinvention, one course I pursue is to maintain a large body of sludge inthe icon-5 ditioning tank for treating the acid waste and in theconditioning tank for treating :the cyanideY waste. Also I maintain alarge body of sludge` in a settling tank which is common to bothindustrial Wastes. The .conditioning tanks are so ar-A ranged thatefuent cannot pass from a tank without passing through the body ofsludge. In accordance with my preferred procedure, I greatly overtreatthe cyanide waste in the cyanide conditioning tank to give lan eiiiuentwhich contains a relatively high alkalinity. effluent from the cyanideconditioning tank in to the acid conditioning tank and then passeiiluent from the acid conditioning tank into the common settling tank.In passage through each of these conditioning tanks, the liquid Wastespass through a large body of sludge and carry some oi the sludge to thesettling tank.

In the accompanying drawings illustrative of installation suitable forthe practice of my invention:

Fig. I is a diagrammatic ovv plan of a cornplete installation forconducting my method ,of Waste disposal, including electrical means forcontrolling the sequential steps of the process.

Fig. 'II is a diagrammatic Aplan view showing a.

group of treating tanks arranged as in Fig. I on an enlarged scale.

Fis. III is a diagrammatic primarily vertical sectional View .of thearrangement of treating' tanks shown in Fig. II. y

Fig. `IV :is a diagrammatic; plan view showing one modification in thearrangement of treating tanks.

Fig. V is a diagrammatic primarily vertical sectional View o1' thearrangement of .treating tanks shown in Fig. IV.

Fig. VI is a diagrammatic plan view showing another modication in thearrangement of treating tanks.

Fig. VII is a diagrammatic primarily vertical sectional View of thearrangement of treating tanks shown in Fig.

Referring initially to Figs. I, Il and III of the drawings, referenceletter A designates a treating tank for cyanide Waste, reference letterB designates a treating tank i'or acid waste and reference letter Cdesignates a common settling tank for both the treated cyanide Waste andthe treated acid waste. Associated with these several treating tanksthere is a cyanide collection tank 4 and an acid colection tank 5. Itwill he I 'pass this assumed that the cyanide is one commonly used inthe plating of metal surfaces, such as the highly poisonous sodium orpotassium cyanides. It also will be assumed that the acid is one of thecorrosive mineral acids used in pickling operations on metals, of whichacids sulphuric acid may be taken as typical. The end result of thetreatment is, as above explained, so to react wastes containing suchsubstances as to render them innocuous.

As above noted the wastes which are sub-jected to treatment are acyanide waste and a mineral acid waste. In my process as hereinafterdescribed the more dangerous cyanide waste obtains in addition to itsindividual treatment the advantage of increased retention as mixed withthe more profuse sludge from the treatment of the acid. As described thesystem comprises individual treating, or conditioning, tanks for each ofthe two diverse wastes and a settling tank common to both.

It should be understood that the process has greater flexibility than ispresented directly in the specific description by which it isillustrated. Thus, the wastes which are treated may be organic as wellas inorganic, such for example as acetic acid waste, the Wastes frompaper-making, tanning and the like which should not be allowed to passinto streams in unaltered condition, but must be brought into a safecondition f approved by supervisory bodies. Also the wastes from otherthan industrial processes can be included properly in the treatment.Thus, for example, sewage and other organic refuse may be treated inaccordance with the process.

Also, it is possible to conduct the process while individually treatingmore than two wastes which receive conditioning reagent from a singlesource; and it is possible to conduct the process while running morethan two wastes into a common settling tank. This primarily involvesmerely duplication of collection tanks, conditioning tanks and controlsand the correlation of those apparatus elements and the wastes subjectedto treatment into the general operation of the A process.

Also taking the illustrative installation as it stands, it is possibleto conduct the process using only one-half of the system up to thesettling tank. In so doing there will be full advantage derived from acontinuously and instantly available supply of reagent and of thecontrol conditions by which the reagent is supplied as the iiow of thewaste to treatment begins, and in which the quantity of such reagent iscontrolled by desired conditions in the conditioning receptacle in whichthe waste is subjected to treatment. Insofar as sludge accumulation inthe settling tank is concerned, in an operation so conducted such sludgewill be supplied by the reactions of the particular waste subjected totreatment, but may be supplemented by sludge derived from previoustreatment in the other half of the system or by arbitrary addition ofsludges.

As the process is hereinafter described, the employed reagents are givenas chlorine and calcium hydroxide solution (milk of lime), as reagentstypical for decomposition of the cyanide and the mineral acid. Even inthe treatment of those particular wastes calcium hydroxide is given asexemplary of a reagent which releases free hydroxyl ions in watersolution and which suitably may be used. In treating wastes of othertypes other reagents may be more desirable.

As commonly resulting from the cyanide treatment of metals, such as ironand steel, there are two forms of cyanide waste. One such form consistsof the cyanide liquor which is discharged from time to time from acyaniding tank. Such waste is highly concentrated. The other form ofcyanide waste consists of the rinse water in which metal from thecyaniding tank has been rinsed, this waste being of course relativelydilute. The same is true with respect to the acid waste, the acid rinsewater being presented for disposal in relatively great volume and theconcentrated acid waste being presented in relatively small volume. Inorder that the process may proceed accurately it is necessary in bothinstances that the dilute rinse Water and concentrated waste be mixed togive uniformity in the concentration of the wastes which are treated. Tomix the total drainage of the vat in which metal is treated with eitheracid waste or cyanide waste with the rinse water at any one time wouldrequire an unduly large pit or collection tank for the mixing.

Collection pit, or tank, l: for the cyanide waste contains primarilycyanide rinse water which is brought to the tank by line 6. A tank 'lfor concent-rated cyanide waste receives that waste by way of line 8 anddelivers it through line 9 to the collection pit, or tank. This line 9is controlled by valve l0 which opens under the influence of float boxll. Similarly, a line I2 brings acid rinse water to acid collection tank5, and that tank also receives concentrated acid waste from a tank i3which receives that Waste by way of a line la and passes it tocollection tank 5 by way of a line l5. Line I5 is under the control of avalve i6 operated by a oat box l1. The concent-rated cyanide waste andthe concentrated acid waste are bled evenly over the operating periodinto the cyanide collection tank 4 and acid collection tank 5 under theinfluence of the respective float boxes Il and l1, each of which isprovided with a nlter and a xed measuring orice. A circulating agitatorI8 operable under the inuence of a timer I9 is provided to insureuniformity in the composition of the waste liquor in collection tank Ll.It is to be understood that either or both tank 1 for concentratedcyanide waste and tank i3 for concentrated acid waste may be of theportable sort. The manner of proportioning the introduction ofconcentrated wastes into the dilute wastes with blending avoids thenecessity of large capacity tanks in order to insure a waste liquor fortreatment which is of uniform concentration and reasonably dilute.

Any of the known reagents suitable for rendering cyanide waste and acidwaste innocuous may be used in conducting a treatment in accordance withthe method of my invention. Assuming, for example, that the typicalreagents chlorine and calcium hydroxide are used, I have found itdesirable automatically to prepare a lime solution and to maintain itunder such conditions as to render it instantly available.

'I'he organization for supplying lime solution for reaction comprises lastorage bin 20 for dryA lime, a lime solution tank 2l and an electricaloperating circuit 22 having a push button contro-ller 23. When circuit22 is energized it operates the motors 24 of twoI cooperative pumps 25which draw solution from tank 2 l by way of line 26 and also energizesmotor 2 la. which actuates an agitator in lime solution tank 2l. Bothpumps communicate with a line 21 one branch 2B of which leads to asupply line 29 and the accesos other branch of whichis a recirculatinglinev 30 returning lime solution` to. tankv 2lI by/way of pressurerelief valve 3 1. These DuJnpsl operate continuously during thefunctioning of the systemto maintainA a constant pressure of the limesolution in lime supply' line 29. A second Yelectrical circuit 32 isenergized by a :doet-controlled switch 33 toopen solenoid valve 34' andadmit waater to the tank byvway of Water line 3'5. Simultaneously itintroduces finely divided' solid lime to the tank from bin 2'@ by theaction of an electrica-lly operated measuring feeder 35. ThisorganizationA automatically insures an adequate supply of limel solutionat all times. during the functioning of the. system, and by keeping thatsolutionl continuously under pressureV renders it instantlyuseful.

Assuming that the system is prepared for operation, with a. pressure of'limes solution built up4 in lime' supply line'E-S and exerting pressureon solenoid-controlled valves 31 and 38 positioned respectivelyy insupply line 29 on opposite sides of its connection with line 28 leadingfrom lime solution tank 2l, andY with cyanide waste and .acid waste intankv 4 and 5 respectively, the system is4 placed automatically inoperation when the liquid level in either or both oi those tanks risesabove a prescribed point.

Referring first to collection tank il' forcyanide waste, aHoet-controlledswitch 3u actsto en ergize electrical circuit 40 and thusto.y initiate a series4 of operations, when' the liouidlevel reaches thepoint' for which the float is set. Thus, energization oi" circuit' 4l)starts motor 4| which actuates pump H2- drawing cyanide. Waste from tank4 into cyanide line d3 and. energizes motor 4'4 which actua-tescooperative draw-oil pump 45. Simultaneously, solenoid valve 3T in limesupply line 29 is opened to permit' lime solution to enter cyanide Une43'. Also simultaneously, chlorine is pumped' into cyanide line 4'3pasty pressure :relief valves 46 in lines 4l from chlorine storage tanks48 by cooperative pumps 49 and` 50 actuated respectively' by motors" 5l"and 52, and a. motor 53 is energized to operatey an agitator` 5f#v (Fig.III) in dovvncomer 55 oicyanide-conditioning tank A. Atthe upper emil ofdowncomer 55 there is a vertically adiustable funnel 55a the adjustmentfwhich influences the extent of the -aeration to which the Waste issubjectedv in. ts

treatment.

Itmay be noted that a second' neat-controlled switch.. 56 operated by afloat placed at a. higher level than. the iioat of. switch 39V acts toenergize the motors of the draw-off pumps and chlorine pumps and tooperate solenoid valve 3l in the lime supply line. and the agitato-r ofcyanide cond'itioning tank AL. This second switch 5S acts if. for anyreason switch 3.9'. should fail' tol `opera-te.

Also operable when the electrical circuit 4U is` energized by eitheroatfcontrolled switch, there is a pli"` controller 5l communicatingelectrically withan electrodea and filter-ing. sampler 59, which lattercommunicates with the. interior of conditioning tank A by. way of. a.duct 60... A switch Si provides for disconnection between the pI-Icontroller and electrode to provide for changing electrodes. Abyepassconnection 52 inlime supplyv line. 29 oy-passing solenoid valve 31,.contains a. solenoid valve 53. to which circuit Ml is completed underthe influence of pHk controller 5l.. Valveal remains open. to supply apredetermined quantity oi" the. lime solution for treating the cyanidewaste. Valve 6.3 opens. intermittently to admit.y additional.lime-solution to the cyanide 5 line at such timesvastheplivalue of Wastetreated. int conditioning tank A'. falls' below aspre-- scribed minimum,

The organization. with respect' to the withdrawal and treatment of acidwaste is identical exceptthat no provision ismade for supplying'chlorine to the line conducting acid waste for treatment from acidstorage tank 5 to acid conditioning tank B. I-Iere also We have aoatcontrolledswitch 64 and a second switch 65 operated by a flo-at setai; a higher level, either of which Switches acts to energize electricalcircuit 66. Energization of circuit 66'. starts the same general seriesof operations as previously' described with respect to the cyanidewaste, en-

ergizing motors 61 and which operate` pumps 65 and 'Hland drawing onacid waste into acid line H- leading to acid conditioning tank B'. Atthe same time solenoid valve 35 in lime` supply line 29 isopened toadmit lime solution toacid line- 1l. Also motor 'l2 which operates an'agitator 13 (Fig. III) in downcorner lli of acid conditioning tank Biss-energized. At the upper end of downcomer lli there is a verticallyadjustable funnel 74a. the adjustment of which inuence's the extent ofthe aeration to which the waste is subjected to treatment.

Also operable vWhen-'the electric circuitis exierg-ized by either flo-atcontrolled switch, there isa pH controller l5`communicating electricallywith an electrode 'I5 and filtering sampler l1, which lattercommunicates with the interior or* conditioning tank B by way of a duct18. A switch le provides'for disconnection between the pIl controllerand electrode to provide for changing electrodes. Valve 38 remains opento supply a predetermined quantity of the lime solution for treating theacid waste. A ley-pass connection all in limesupplyfline- 29'ley-passing solenoid valve 33 contains a. solenoid valve 8l to whichcircuit 66 is completed by' pl-I controller 15. Valve 8|thus.-opensintermittently to admit additional-lime solution to acid linell at such times as the pI-I value of Waste loeingy treated inconditioning tank B falls below a prescribed minimum.

Cyanide waste entering cyanide conditioning tank A -by wayA of cyanideliney d3' enters downcomerV 55 of' the tank and passes downwardlytherethrough, being agitated' in. passage by agitator 54. It is to beunderstood thatV with this cyanide Waste there is included liniesolution entering line L13' by way of lime supply line 2.9 and'.chlorine entering cyanide line All by way of chlorine supply line lll'.In Figs. Il andlII- the position andv arrangement of the linie supplyline andthe lchlorine supply line is'simplied to bring those .linesintoA the illustration of' those gures oi the drawings. In passage ofthe cyanide Waste downwardly in downcomer 5.5 o"v the.cyanideconditioning tank, the` waste is aerated' by air inducedovcr'thelip of tunnel' liliaby the action ofagitator 5ft. In thedowncoiner the' reactions which have begun in cyanide line 43 are'continued. and upon issuance of the waste undergoing treatment lfrom.the lower end oi' downcomer 55 intotlie outer chamber 8.2 .ofconditioning tankv A, it meets. and is vigorously mixed' witha volumeofv sludge which is allowed to build up at the base of the tank. As thelevel of liquidI rises. in cyanide conditioningtank A because ofaeration and' incoming waste it passes over a' sau/toothed overflow 83into an annular trough dlfrom which it passes as eiiuent to settlingtank C..v This cfiiuentV waste, which is highly aerated',

'carries with it into tank C some of the alkaline sludge with which itis mixed in conditioning tank A.

Acid waste entering acid conditioning tank B by way of acid line 1lenters downcomer lll of the tank and passes downwardly therethrough,being agitated and aerated in passage by agitator 13. It is to beunderstood that with this acid waste there is included lime solutionentering acid line 1i by way of lime supply line 2S. In Figs. II and IIIthe position and arrangement of the lime supply line is simplified tobring that line into the illustration of those figures of the drawings.In passage of the acid waste downwardly in downcomer M of the acidconditioning tank, the reactions which have begun in acid line 'Il arecontinued. In the downcomer and upon issuance of the waste undergoingtreatment from the lower endof downcorner 'l into the outer chamber 85of acid conditioning tank B it meets and is vigorously mixed with avolume of sludge which is allowed to build up at the base of the tank.As with the cyanide waste, the acid waste is aerated by air which isinduced as liquid flows into the downconier over the lip of funnel 'Mafor recirculation. As the level of liquid rises in acid conditioningtank B because of aeration and incoming waste, it passes over asaw-toothed overflow 85 into an annular trough 8l from which thiseffluent water passes to settling tank C, carrying vwith it some of thealkaline sludge from tank B.

In both conditioning tanks the mixture of waste undergoing treatment andthe reagent together with accumulated precipitates is subjected to anaeration which accelerates the treatment. The aeration is effected byinduction of air as liquid from the outer chamber of the tank is liftedover the lips of the funnels at the upper ends of the downcomers forrecirculation. Thus the level to which a funnel is adjusted controls thevolume I" recirculated liquid mixture and the air induced by therecirculating inflow` This intimate blending of the wastes and chemicalprecipitates accompanied by foaming and recirculation assures aneiectively complete destruction of the original properties of thewastes. When operating in tanks of a size which may be considered normalfor full scale operation, the sludge accumulation in the tanks whenquiescent should have a depth of several feet.

Line 88 leading from annular trough 84 of cyanide conditioning tank Aenters an annular downcomer provided between the wall of inner downcomer89 and an outer shell 96 in settling tank C. Passing downwardly throughthis annular space to its opening in the lower region of tank C, cyanidewaste enters a body of sludge carried over from both the cyanide andacid conditioning tanks, or formed by completion of the reactions in thesettling tank. Eiiiuent from annular trough 81 of acid conditioning tankB passes by way of line 9| to a space ywithin the inner downcomer 89 ofsettling tank C and passing downwardly through this downcomer alsoenters the body of sludge collected in the bottom of the tank. A motor92 rotates a shaft 93 which carries blades 93a positioned below thelower ends of the downcoiners. Such blades are rotated very slowlymerely to produce some movement in the sludge toward the center of thetank and thus to facilitate its intermittent Withdrawal from the tank.As the level of liquid in cuter chamber 94 of settling tank C rises withcontinued operation oi the system, it passes over the saw-toothedoveriiow 95 into an annular sump 96 from which it ilows as harmlesseffluent by way of a draw-off line 91.'

At the base of conditioning tanks A and B and settling tank C there arerespectively valved draw-off lines 98, 99 and |09 which may be used tomaintain a suitable level of sludge in the several tanks. If thecharacter of the sludge in cyanide conditioning tank A should bequestioned, such sludge can be corrected with sludge from acidconditioning tank B before its transfer to settling tank C to becomepart of the mixed sludge at the base of that tank. Also, if desired,sludge may be transferred from settling tank C to supplement the sludgeprecipitated in either of the conditioning tanks A and B or sludge fromone of those tanks can be transferred to the other of said tanks tosupplement the sludge formed therein. In practice the discharged sludgeis collected in tank trucks and delivered to a dump.

The reactions involved in rendering the specifically indicated wastesharmless will now be described. As cyanide waste is taken from thecyanide collection tank and fiows through the cyanide pump-line tocyanide conditioning tank A, it receives in passage a charge of calciumhydroxide and of chlorine, carrying these reagents with it into thedowncomer of the cyanide tank and being thoroughly mixed with thereagents by agitation in the tank. The reactions begin in the cyanideline and continue into the cyanide conditioning tank. As the reactionstake place, reaction products are precipitated to form the sludge in thecyanide conditioning tank. These reactions may be illustrated asfollows:

This reaction takes place very rapidly and by it the intensely poisonouscyanide is converted to the relatively harmless cyanate.

Although these cyanates such as sodium cyanate and potassium cyanatehave only about IAOOO the toxicity of the corresponding cyanides, thecyanate is itself destroyed by continued reaction with an alkali andchlorine as in accordance with the illustrative formula:

The iirst reaction given above, which is the reaction vprimarilyeffective in `destroying the toxic properties of the cyanide Waste, issubstantially complete within about one or two minutes under conditionsof alkalinity exceeding a pH of 8.5. The second reaction takes placewithin an hour. These are accepted reactions in accord- -ance `withliterature references. The actual operation of the method as hereindisclosed was checked under pilot plant conditions. Under thoseconditions the results indicated that the rst reaction was completeWithin one minute on waste having an initial 100 p. p. m. cyanideconcentration. The second reaction was about 80% complete within twohours and the toxicity of the cyanate being relatively so low thereactions were considered in practical effect completely to havedestroyed the toxicity of the cyan1de lwaste. During the test ofalkalinity in the cyanide conditioning tank it was maintained at a pH ofabout 8.7. During the operation of the process as conducted the pHin thecyanide conditioning chamber is therefore to be understood as maintainedin excess of a pH of 8.5.

.Assurance of adequate treatment of the cyanide waste in itsconditioning tank is assured by mixing the reacting waste with aconsiderable body of the sludge precipitated in the tank. l'

aardse? The treatment fof the acid'lwaste is 1close1y similar. Acidwaste vtrom -tlre -acid collection -tank :or pump-pit in its passa-getop-'acid conditioning tank l5; receives a charge of lime solution withwhich it enters the downeomer of the tank and is thoroughly mixed for4reaction 'with the lime solution during passage through the-downvcomer-to the lower region'o'f the tank. The vpri- 'mary'reaction isoneofthe wellknown neutralizing reactions, such as:

Mixed lwith the precipitated CaSOi there are precipitatesof metalhydroxides such as 'the-hydroxides of iron, nickel andchromelgo'ing tofforrn the `sludge `in `the'lower regionvof'fthe acid conditioning tank.4In this 'tank vthe alkalinity is maintained at a -pH inlexcess lof fr,such as "a pH of 7.5 andhigher.

During 4the `operation of 'the method, flow of llime solution to boththe cyanide conditioning tank and -the acid conditioning -tank yisjquantita- 'tively under the control of p-I controllers v5l fand "V5'the passage or Achlorine to the cyanide conditioning tank beingregulated "by 'the setting of `Valve '56. Whereas the introduction ofthe llime solution is proportioned'according 'to the pH, 'theintroduction of chlorine is kcontinuous under the 'action of motors 51and l'52 on pumps il@ 'and forcing chlorine :from tanks 48 past valvesd'6. The great advantage of placing the ilow lofi-lime 'underthe'influence of 'the pH controllers is twotold. From one .aspect`it'assures that there vbe sufficient 'alkalinity 'in the conditioning'tanks 'to carry out the necessary reactions therein. From anotherviewpoint -it assures 'that the necessary results be obtained with aminimum ofthe reagents whichrender'the wastes harmless; it 'being`imderstoodfthat the vmaintenance ofproper alkavlinity in the cyanideconditioning tank assures vcomplete utilization of the chlorine Whichispro- 'Vided and lthus additionally limits .the excess of .are renderedwholly innocuous. The lpresence' V of the substantial `bodies lof.slu'dges rin the two Aconditioning tanks and in the .common settling.tank 4fullyprotects the system against 4slugs #of wastes having ahigher than normal concentration of toxic components. ance of slugs isguarded against 'initially by the dolending or concentrated Wastes from'actual Ypickling and cleansing 'operations with the wash waters "fromthose operations, it is possible that there fmay 'be vsome temporary orlocalized increase in the concentration of the ytoxic ingredients and-against such conditions the vpassage of wastes undergoing treatmentthrough thesludges "gives Aprotection without ymaintaining .anexorbitantly great excess o'f .reagents in the system. Because of the.fact that the system is under automatic control the possibility `of--difculties rising vfrom human errors and omissions iis Treduced mto aminmum.

Although the 'avoid- A valved return line lili of trough 9S #of` thesettling tank leads 4to pumps and 50 ywhich Vforce chlorine from tanksand. past Valves lf3 rication resides in the arrangement of fthe twovconditioning tanks andthe settling tank and the alteration of thesequence of steps-so caused. The

'modified course followed by thewastes in 4accordance with this Variantci' the process is illustrated `by the arrangement oicyanideconditioning tank D, acid-conditioning tank E and 'settling tank'F whichcorrespond in structure though not -in'arrangement to the analogoustanks A, vE, and@` as previously described.

"Thus 'as shown in Figs. 1V and V cyanide line 'd3 leads todowncom'erE62 in cyanide conditioning tank-D, the connection of lime supply line29 and chlorine supply line il to this tank being similar to likeconnections to cyanideconditioning tank A. Similarly an agitator |633 ismounted in downcomer lili hai/ing a vertically-adjustable funnel Etta atits upper end and thedowncomer empties adjacent the lower region of thetank into the bottom and outer chamber IEM of 'the tank. A valveddraw-ciline H5 for "sludge is provided at the base of the tank. Similarly tocyanide'conditioning tank yiik, tank D isequinp'e'd with a saw-toothedoverflow H35 over 'which treated water passes into annular trough "I-'when 'the level of liquid rises'sulciently'in ithe tank. Similarly tocyanideconditioning tank A, cyanide conditioning tank D is equippedwitha 4pHvcontroller 'ii inelectrical control circuit-40. The pHcontrollercommunicatesfelectricallywith `an electrode LIB 'and*filtering sampler liiwhich latter communicates with 'the interior oflconditioning tank D by way of a'duct Nil. A switch iH l provides fora-disconnection between th'epH controller andfthe'elec'trode-to providefor chang- Ving electrodes. Instead of passing directly to Aa. settlingtank, however, draw-0H line |12 f1-oni .annular trough -iili of thevcyanide `conditioning tank empties-into dcwncomer ||3 ofacidconditioning tank E.

Thistank similarly is equipped with agitator |`|4"indownccmer N3,vertically adjustable funrnel i3d at lthe upper lend of the downc'omer,

-valved draw-offline for sludge I5, `a'saw-toothed overflow i-'l at theupperend of outer chamber lf'll' of the tank from 'which theupper'levelof liquid passes into annular vtrough Hl). `Italso similarlyequipped with pH controller Iii-9, :electrode |129, altering sampleritiand-'disconnecting switch |22. The plelicontrolleris incommunica- -ti'onwith `the general electrical control 'circuit 66 'of the system. Line *Hconducts acid'wastes Aand lime solution to downconier `H3 to meettreated lcyanide5wastefdelivered 'by `draw-'onf line "I f2 *fromfcyanideconditioning ltank D.

nro-m .the annular trough iis of acid condi- .fti'oning tank E adraw-off line |23 .leads 'to 'the downcomer 121i! of settling "tankE-tSettlin'g tank tE iissimilarmoonstructioirtofsettling'tarik Cprej-Wiouslydescribed. iikes'ettlingtankC it 'has 'a `wah/'eti tiraweoifconnection :|125 y'for 'excess 'sludge and an agitator 26 which isslowly motor driven to move sludge by means oi blades iEEa toward thecenter of the tank at its base. Settling tank E also has in its upperregion a saw-toothed overilow |21 over which the upper level of liquidin the outer chamber |28 of the tank flows into annular trough |29. Adraw-oli line |3 withdraws eiiluent from trough |23. It is to beunderstood that a second valved line similar to the valved return lineshown in I can be provided either as independently connected with trough|23 or as a branch of draw-off connection |30 to recirculate eluentthrough chlorine pumps 49 and 5i) and storage tanks 43. into cyanideline 43 leading to cyanide conditioning tank D,

The modincation of the method as illustrated by the apparatusarrangement suitable for its practice shown in Figs. IV and V of thedrawings is preferred procedure. In conducting this variant of themethod the pH controller associated with the cyanide conditioning tankis set to maintain a high excess alkalinity in that tank to the extentof maintaining a pH of ll or even higher. This places the emphasis ofthe process on the destruction of the highly toxic cyanide waste whichreceives initially a very great overtreatment. The excess alkalinityfrom this overtreatment serves to treat the acid waste in the acidconditioning tank. Because the reactions by 4which the initial cyanidecontent of the cyanide waste is destroyed are irreversible this can bedone with complete safety insofar as the cyanide waste is concerned. Asadditional assurance, however, that the wastes oi both types will berendered innocuous the pH controller of acid conditioning tank Emaintains in the acid conditioning tank `an alkalinity, such as isindicated .by a pH in excess of 7.5, adequate to insure completetreatment of the acid waste as well as the cyanide waste. As in thepractice previously described this is done by introducing an alkalinereagent such as lime solution into the acid line leading to tank E atsuch times as the pI-I in the tank tends to drop.

It will be noted that in this modication of the process, also, wastes ofboth kinds pass to a common settling tank before being discharged aseiu- `ent. Thus in this modication, also, both wastes undergoingtreatment are mixed at least twice with bodies of alkaline sludge in theseveral tanks andthe cyanide waste is mixed three times with sludgebefore being discharged as eliluent. As explained above, this repeatedmixture with sludge insures against the inclusion of imperfectly treatedwaste in the ultimate effluent under abnormal conditions in which slugsof increased vconcentration pass through the system. With respect to thedangerous cyanide wastes this modiication also provides a sludgeadmixture addition to that provided by practice of the method asillustrated in Figs. I to III of the drawings. As in the procedureapplicable to Figs. I to III, the use of a settling tank common to thewastes of both kinds insures an adequate volume of sludge in the finaltank of the system and gives to the dangerous cyanide `waste theadvantage of nal treatment in a body of sludge to the formation of whichthe precipitation of products from treatment of the acid waste hascontributed.

The method as conducted in accordance with the procedure illustrated inFigs. VI and VII is identical with the method as described in connectionwith Figs. IV and V of the drawings. The only diierence involved in theshowing of Figs. VI and V11 is in the telescoping of apparatus tosimplify the installation in which the 12 plant space required forinstallation. Here again it is to be understood that all the elementsand controls associated with the conditioning and settling tanks asshown in Fig. I of the drawings are present in an installation havingthe arrangement of conditioning and settling tanks shown in Figs. VI andVII.

Referring to the apparatus as shown in Figs. VI and VII of the drawings,this apparatus comprises a cyanide conditioning tank G, an acidconditioning tank H and a settling tank I, the acid conditioning tank Hbeing arranged within settling tank I. Thus cyanide conditioning tank Gcomprises a dcwncomer |3| equipped with a vertically adjustable funnel|3|a at its upper end and with a motor driven agitator |32 and a valveddraw-off line for sludge |33. Cyanide line 43 in communication with limesupply line 29 and chlorine line 41 opens into the upper end ofdowncomer |3I. Similarly to the analogous tanks which previously havebeen `described cyanide conditioning tank G is shown as provided with asaw-toothed overflow |34 over which liquid rising in the outer chamber|35 of the tank passes into annular trough |36.

The combination of acid conditioning tank H and settling tank Icomprises a downcomer |31 having a vertically adjustable funnel at itsupper end into which discharges draw-off line |38 for eiiluent from thecyanide conditioning tank. Acid line 1|, to which connection with limesupply line 29 is shown, also discharges into downcomer |31. Indowncomer |31 there is a motordriven agitator |33 and at its lower endthe downcomer opens into a downwardly closed receptacle which serves asthe acid conditioning tank H. Surrounding downcomer |31 there is abailie sleeve |40 which extends to the upper end of the tank andsurrounding acid conditioning tank H there is a second baiiie sleeve |4|which also extends to the upper end of the tank. It will be noted thatthe upper and receiving end of downcomer |31 lies above the upper end ofthe acid conditioning tank H and is equipped with vertically adjustablefunnel |31a. In the upper region of the settling tank I in the outerchamber |42 thereof and surrounding outer baffle sleeve |4| there is asaw-toothed overiiow |43 over which the upper level of liquid in thesettling tank can flow into annular trough |44. A draworf line |45receives eiluent from trough |44 and it will be understood that a returnline for conveying eiiluent to the chlorine pumps desirably also isprovided as shown in Fig. I of the drawings and as above discussed.Similarly to the conditiomng tanks as previously disclosed a pHcontroller is associated with cyanide conditioning tank G and with acidconditioning tank H standing within settling tank I. Thus, as shown,cyanide conditioning tank G has associated therewith a pH controller |46in communication with electrical control circuit 40 and with anelectrode |41 and a filtering sampler |48 communicating with theinterior of the tank. A switch |49 provides for disconnection betweenthe pl-I controller and electrode to provide for changing electrodes.Similarly acid conditioning tank H has associated therewith a likeorganization of pI-I controller |50 in communication with electricalcontrol circuit 66, an electrode |5|, a ltering sampler |52 and switch|53 for changing electrodes.

Cyanide waste entering cyanide conditioning tank G is treatedidentically as in cyanide conditioning tank D shown in the apparatusorganization of Figs. IV and V, excess alkalinity to the extentrepresented by a pH-off 11 or over beagecogcor ing Vmaintained in thetank. -Eiuent from 'the Ycyanide conditioning tank passing intodowncomer -l 31 in the acid "conditioning tank and settling tankassemblymeets -With acid "Waste and isthoroughly mixed v.Within theacidconditioning tank, the-excess alkalinity of Ethe'cyanide wasteundergoing treatment providing :neutralizing reagent for the acid Waste.As in acid conditioning tank `E of Figs. lV-and V, the pHcontroll'er ofacid -conditioning t'ank-il-Iv 'serves' tomain'tainralkalinityfataVsuitable 'Value in excess fof 7*.5 lin the acid conditioning tank.

As the level of-liquidinthefdowhwardlylclosed acid conditioning tank'rises, that liquid hows over the lip of vthe tankinto "the annularvspace between the 'wall of .the ltank and outer baliies fili anddownwardlyinthat space tothe bottom and'outer chamber'ofsettling tankl.Underth'e inuenc'e 'of `agitator 139 4sludge 'also is carried over thelip of acid'conditioning tank Hand'into the 'settling tank I. Whensettling 'tank 'I :has lined, `the liquid whichfas in other' variants'of my process consists of Aclear .and harmless water, flowsoversaw-toothed overow M3 into annular trough M4 and -is discharged .asYeilluent .through line |45 or is recirculated back Ato the chlorinepumps. It should be noted that sludge as Well aslq'uid is'carried overthe lipfof acid conditioning tankl-I and passes to the bottom 'ofsettling tank I. A suitable .level of sludge yin thefsettling .o

tank is maintained by drawing-off sludge from .time to time by Way ofvalved discharge line 154. It is thus clear that lthe conduct of themethod in the organization of Figs. VI and lVII is identical with themethod as conducted vin the apparatus of Figs. IV and V.

:Considering the process purely :as a Achemical process apart from thedisclosed automatic controls, it consists in separately treating two di--verse wastes, one'of which is .more toxic than the other and both ofwhich originate in the lform both 7Vof concentrated Waste 'and dilutewaste. In preparation for-reaction these Wasteseachai'e blended by acontinuous operation, `toobtain-uniformity of vdilution undercondition'scso Ycontrolled that the likelihood of deliver-y of la -wastein .its more concentrated form lfor :reaction is minimized. As each ofthe Wastes in its blended form hows to treatment it 'is charged with areagent, or reagents, appropriate for reactions which render the wasteinnocuous. These nblended and charged 'wastes are then treatedseparately with repeated agitation and aeration in admixture withsludge, which sludge typically is composed of the products Vof thereaction 'by which the wastes aredecomposed and contains an'exc'ess ofthe decomposing reagent. After reaction 4With agitation and aeration fora period suiicient under normal circumstances to lrender the Wastesharmless, they both pass as eliiuerit to a'commo'n settling receptaclein which the effluents mix with a body of sludge'in'thesettlingreceptacle and remain .for a further retention period under `conditions4in which there is an `eacessvof the Adecomposing reagent, until theyiinally Dass as a common and harmless eluent from the settling tank.

As a preferred modication of this process, there beine; a reagentappropriate to the treatment of both the said Wastes, the more ltoxic ofthe two wastes is treated with a great excess of the common reagent. Theeffluent from this Waste then carries an excess of that common reagentto a receptacle in which such excess is employed in treating the secondWaste. In this reaction additional reagent is supplied if necessary inorder to assure complete decomposition of Cil lili both wastes `line'combined Ysituent thenfpasses from the second receptacle-'to la'sttlingreceptacle for fur-ther retention .and ultimate discharge.

Considered llfrom the 'viewpoint of automatic control'as 'Well as ofpurely chemical process, a supply of -the reagent which :is commontoit-he Wastes of -bo'th ity-'pes is mai-ntainedunder con- -stan'tipressure for instantaneous addition to the 'Wastes in their passage vtotreatment. Addition of this common reagent is made `lauto'matically andinstantaneously under 'the 'influence lof the electrical controls 'whichinitiate -owio the wastes to their individual treatments. lIn.conjunction -lW'ith the initial blending of eachof the 'Wastes v'withvrespect Ito its `concentrated ian-'d `dilute occurrence, thislinstantsupply of reagent prevents `lthe passage 'oi vslugs of Vraw lwaste Jtovtreating receptaclesfapart-from'the reagent 'with Vwhich that Wasteisto be reacted. Further controls 'automatically Y supply such quantity"of the additional reagent vaslmay be required vtomaintain conditionsappropriate to the cornplete decompositionv of the 'two wastes in their.initial treatment. 'These .controls are 'suchastom'aintainnexces's ofreagent in eilluent lfr'omthe .initial 'treatments passingto the common`settling container.

It will be understood that it may be desirable even though there befonly'one 'particular Waste to be subjected-to treatmentthatth'esupply .ofsuchwa'ste `loe dividedffor initialftreatment, ibut that theyetfluen't's from the 'initial 'treatments lloe brought together for alcomm-'on settling `,xreriod before an ultimateeiuentis discharged..Also that any number of diverse Wastes initially treated may be brought"to a vc'orr'irnon settling tank and maintained under such chemicalconditions as give additional assurance as to 'the harmless nature ofthe comldined effluent. In either case,orfi`f an individual wasteislsimpl-y to be treated by itself-as in one-halfentheltreating system,the automatic blending is of importance when the Wasteoccurs'both inconcentratediand dilute form. Also -suchblendingmay userully bepracticed on unlike wastes both-of Which-canbe 4completely treated yby'a "common reagent and one "of which is *of 'such nature Ytha'jt`blending with the other bef-oretreatmentis"advantageous, 'n'any 'event'automatic Icontrol byiv'vhich reagent "in sudcient quantity is suppliedinac'cordance with 'the condition of the waste undergoing 'treatmentisan importanteature.

Icla'iin as"my invention:

v1; The method of treating'two 'Waste Waters l`from industrialoperations v4which 'waters respectively contain .in 'solution diversetoxic sub- Xsta'nces, the said dissolved'substance in one'sa'id waterexceedi*ng thatoftne'uth'erwaterfin'toxiaity, "the reactions "forrendering which 4toxic substances 'harmless involving at least one`common reagent, by v Hot/ing .the Said `S`1lt0h`svlfb`m volumes of.supply thereof "to reaction chambers `therefor, 'throughout the iiow ofsaid "solutions Asupplying to each thereof reactive material containingthe common reagent capable of rendering the toxic substance of the saidsolution harmless by reaction therewith, the amount of reaction materialadded being suicient to supply a substantial excess of said commonreagent to the solution containing the toxic substance of 4greatertoxicity, owing eiiluent containing excess of the said common reagentfrom the reaction chamber for the solution having a toxic conjtent ofgreater toxicity into the reaction chamber for the solution having thetoxic content of lesser toxicity, and following reaction in said lastnamed reaction chamber settling the mixed reacted solutions and thesolid products of reaction therein and drawing off eiuent therefrom.

2. The method of treating two waste waters from industrial operationswhich waters respectively contain in solution a mineral acid and acyanide, the reactions for rendering which toxic substances harmlessinvolving as a common reagent a substance capable of supplying freehydroxyl ions in Water solution by owing the said solutions from volumes0f supply thereof to reaction chambers therefor, throughout the flow of.said solutions supplying to each thereof reactive material capable yofrendering the toxic substance of the said solution harmless by reactiontherewith, the said hydroxyl ion supplying substance being added to bothsaid solutions and chlorine being additionally supplied to the saidcyanide solution, the said hydroxyl ion supplying substance as a commonreagent lbeing added in substantial excess to the solution containingcyanide, iiowing eliiuent containing excess of the said common reagentfrom the reaction chamber for the cyanide solution into the reactionchamber for the mineral acid solution, and following reaction in saidlast named reaction chamber settling the mixed reacted solutions and thesolid products of reaction therein and drawing off eiiiuent therefrom.

3. The method of treating two waste waters from industrial operationswhich waters respectively contain in solution diverse toxic substancesthe said dissolved substance in one Said water exceeding that of theother said water in toxicity, the reactions for rendering which toxicsubstances harmless involving at least one common reagent, at least oneof said waste waters occurring in the form of a relatively dilute and arelatively concentrated solution of the toxic substance therein, in thereceptacle containing a volume of supply of the said dilute solutionautomatically iiowing off suicient solution from the volume of supply toa reaction chamber on inflow of the more dilute solution to maintain aconstant level of solution in the receptacle containing said volume ofsupply, continuously making a blend of the said more dilute andconcentrated solutions by bleeding the more concentrated solution of thesaid toxic substance into the more dilute solution thereof during flowfrom the said volume of supply, flowing the said diverse solutions eachto a reaction chambertherefor, throughout the flow of said solutionsautomatically supplying to each thereof reactive material, containingthe common reagent, capable of rendering the toxic substance 0f the saidsolution harmless by reaction therewith, the amount of reaction materialadded being suicient to supply a substantial excess of said commonreagent to the solution containing the toxic substance of greatertoxicity, flowing eiiiuent containing excess of the said common reagentfrom the reaction chamber for the solution having a toxic content ofgreater toxicity into the reaction chamber for the solution having thetoxic content of lesser toxicity, and following reaction in said lastnamed reaction chamber settling the mixed reacted solutions and thesolid products of reaction therein and drawing oii effluent therefrom.

4. The method of treating two waste waters from industrial operationswhich waters respectively contain in solution a mineral acid and acyanide, the reactions for rendering which toxic substances harmlessinvolving as a common reagent a substance capable of supplying freehydroxyl ions in water solution, at least one of said waste watersoccurring in the form of a relatively dilute and a relativelyconcentrated solution of the toxic substance therein, in the receptaclecontaining a volume of supply of the said dilute solution automaticallyflowing off sufiicient solution from the volume of supply to a reactionchamber on inflow of the more dilute solution to maintain a constantlevel of solution in the receptacle containing said volume of supply,continuously making a, blend of the said more dilute and moreconcentrated solutions by blending the more concentrated solution of thesaid toxic substance into the more dilute solution thereof during flowfrom the said volume of supply, flowing the said diverse solutions eachto a reaction chamber therefor, throughout the flow of said solutionssupplying to each thereof reactive substance capable of rendering thetoxic substance of the said solution harmless by reaction therewith, thesaid hydroxyl ion supplying substance being supplied to both saidsolutions and chlorine is additionally suppliedto the said cyanidesolution, the said hydroxyl ion supplying substance as a common reagentbeing added in substantial excess to the solution containing cyanide,owing eiiluent containing excess of the said common reagent from thereaction chamber for the cyanide solution into the reaction chamber forthe mineral acid solution and following reaction in said last namedreaction chamber settling the mixed reacted solutions and the solidproducts of reaction therein and drawing oi eiuent therefrom.

CYRUS WM. RICE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,194,933 Barber Aug. 15, 1916 1,418,013 Newman May 30, 19221,824,935 Travers Sept. 29, 1931 1,928,163 Barnard Sept. 26, 19332,194,438 Wernlund et al Mar. 19, 1940 2,348,124 Green May 2, 1944FOREIGN PATENTS Number Country Date 538,929 Great Britain Aug. 21, 1941

1. THE METHOD OF TREATING TWO WASTE WATERS FROM INDUSTRIAL OPERATIONS WHICH WATERS RESPECTIVELY CONTAIN IN SOLUTION DIVERSE TOXIC SUBSTANCES, THE SAID DISSOLVED SUBSTANCE IN ONE SAID WATER EXCEEDING THAT OF THE OTHER WATER IN TOXICITY, THE REACTIONS FOR RENDERING WHICH TOXIC SUBSTANCES HARMLESS INVOLVING AT LEAST ONE COMMON REAGENT, BY FLOWING THE SAID SOLUTIONS FROM VOLUMES OF SUPPLY THEREOF TO REACTION CHAMBERS THEREFOR, THROUGHOUT THE FLOW OF SAID SOLUTIONS SUPPLYING TO EACH THEREOF REACTIVE MATERIAL CONTAINING THE COMMON REAGENT CAPABLE OF RENDERING THE TOXIC SUBSTANCE OF THE SAID SOLUTION HARMLESS BY REACTION THEREWITH, THE AMOUNT OF REACTION MATERIAL ADDED BEING SUFFICIENT TO SUPPLY A SUBSTANTIAL EXCESS OF SAID COMMON REAGENT TO THE SOLUTION CONTAINING THE TOXIC SUBSTANCE OF GREATER TOXICITY, FLOWING EFFLUENT CONTAINING EXCESS OF THE SAID COMMON REAGENT FROM THE REACTION CHAMBER FOR THE SOLUTION HAVING A TOXIC CON- 